New reaction chamber for transient field g-factor measurements with radioactive ion beams

A new reaction chamber has been designed and constructed to measure g-factors of short-lived excited states using the Transient Field technique in combination with Coulomb excitation in inverse kinematics. In this paper we will discuss several important aspects which have to be considered in order to successfully carry out this type of measurement with radioactive ion beams, instead of the stable beams used in a wide range of experiments in the past. The technical solutions to the problems arising from the use of such radioactive beams will be exposed in detail and the first successful experiment using the new chamber in combination with MINIBALL cluster detectors at REX-ISOLDE (CERN) will be reported on.status: publishe

Low-velocity transient-field technique with radioactive ion beams: g factor of the first excited 2+ state in 72Zn

The g factor of the first excited 2+ state in 72Zn has been measured using the transient-field (TF) technique in combination with Coulomb excitation in inverse kinematics. This experiment presents only the third successful application of the TF method to a short-lived radioactive beam in 10 y, highlighting the intricacies of applying this technique to present and future isotope separator on-line facilities. The significance of the experimental result, g(2+ 1 ) = +0.47(14), for establishing the structure of the Zn isotopes near N = 40 is discussed on the basis of shell-model and beyond-mean-field calculations, the latter accounting for the triaxial degree of freedom, configuration mixing, and particle number and angular momentum projections.status: publishe

Quadrupole collectivity in neutron-rich Cd isotopes

The investigation of the excitation energies of the 21+ –states in the neutron-rich Cd isotopes shows an irregular behaviour when approaching the neutron shell-closure at N = 82. The energy of the 21+–state in 128Cd is lower than the one in 126Cd. The transition strength B(E2, 0gs+ → 21+) in the even isotopes 122−128Cd was measured in Coulomb excitation experiments with the high-purity germanium detector array MINIBALL at REXISOLDE (CERN). The values for 122,124Cd coincide with beyond-mean-field calculations with a resultant prolate deformation, whereas 126,128Cd are better described by shell-model calculations

Quadrupole collectivity in neutron-rich Cd isotopes

The investigation of the excitation energies of the 21+ –states in the neutron-rich Cd isotopes shows an irregular behaviour when approaching the neutron shell-closure at N = 82. The energy of the 21+–state in 128Cd is lower than the one in 126Cd. The transition strength B(E2, 0gs+ → 21+) in the even isotopes 122−128Cd was measured in Coulomb excitation experiments with the high-purity germanium detector array MINIBALL at REXISOLDE (CERN). The values for 122,124Cd coincide with beyond-mean-field calculations with a resultant prolate deformation, whereas 126,128Cd are better described by shell-model calculations.status: publishe

Enhanced Quadrupole and Octupole Strength in Doubly Magic 132Sn^{132}\mathrm{Sn}

The first 2^{+} and 3^{-} states of the doubly magic nucleus ^{132}Sn are populated via safe Coulomb excitation employing the recently commissioned HIE-ISOLDE accelerator at CERN in conjunction with the highly efficient MINIBALL array. The ^{132}Sn ions are accelerated to an energy of 5.49  MeV/nucleon and impinged on a ^{206}Pb target. Deexciting γ rays from the low-lying excited states of the target and the projectile are recorded in coincidence with scattered particles. The reduced transition strengths are determined for the transitions 0_{g.s.}^{+}→2_{1}^{+}, 0_{g.s.}^{+}→3_{1}^{-}, and 2_{1}^{+}→3_{1}^{-} in ^{132}Sn. The results on these states provide crucial information on cross-shell configurations which are determined within large-scale shell-model and Monte Carlo shell-model calculations as well as from random-phase approximation and relativistic random-phase approximation. The locally enhanced B(E2;0_{g.s.}^{+}→2_{1}^{+}) strength is consistent with the microscopic description of the structure of the respective states within all theoretical approaches. The presented results of experiment and theory can be considered to be the first direct verification of the sphericity and double magicity of ^{132}Sn.status: publishe

Coulomb excitation of pear-shaped nuclei

status: Published onlin

Single-neutron orbits near 78Ni: Spectroscopy of the N=49isotope 79Zn

Single-neutron states in the Z=30, N=49isotope 79Zn have been populated using the 78Zn(d,p)79Zn transfer reaction at REX-ISOLDE, CERN. The experimental setup allowed the combined detection of protons ejected in the reaction, and of γrays emitted by 79Zn. The analysis reveals that the lowest excited states populated in the reaction lie at approximately 1MeV of excitation, and involve neutron orbits above the N=50shell gap. From the analysis of γ-ray data and of proton angular distributions, characteristic of the amount of angular momentum transferred, a5/2+configuration was assigned to a state at 983keV. Comparison with large-scale-shell-model calculations supports a robust neutron N=50shell-closure for 78Ni. These data constitute an important step towards the understanding of the magicity of 78Ni and of the structure of nuclei in the region.publisher: Elsevier articletitle: Single-neutron orbits near 78Ni: Spectroscopy of the isotope 79Zn journaltitle: Physics Letters B articlelink: http://dx.doi.org/10.1016/j.physletb.2014.12.006 content_type: article copyright: Copyright © 2014 The Authors. Published by Elsevier B.V.status: publishe

Investigation of Low-lying States in 133Sn Populated in the β Decay of 133In Using Isomer-selective Laser Ionization

Excited states in the neutron-rich isotope 133Sn were studied via the β decay of 133In. Isomer selective ionization using the ISOLDE RILIS enabled the β decays of 133Ings (Iπ = 9∕2+) and 133mIn (Iπ = 1∕2−) to be studied independently for the first time. A description of the experimental setup at the ISOLDE Decay Station is presented together with preliminary results from the experiment.status: publishe